A cage has the purpose of separating the rolling elements so that no mutual rolling element contact occurs and so that the rolling elements are evenly distributed around the bearing.
It is important for the proper function of the bearing that the contact forces between the cage and the rolling elements are as small as possible at the same time as the cage is allowed to perform its duty. There are various causes for the rolling elements to influence the cage. For example, misalignment between the outer and the inner ring of the bearing will change the shape of the orbit of the rolling elements, whereby the rolling elements impose axially directed forces on the cage. In a radially loaded bearing, the orbital speeds of the rolling elements are different in loaded and in unloaded zones of the bearing, whereby the distances between the rolling elements vary during operation. This fact causes the rolling elements to impose peripherally directed forces on the cage. Further, because of unavoidable manufacturing tolerances the rolling elements in a bearing are always of unequal sizes, which means that they tend to have unequal orbital speeds with the result that the cage is subjected to peripheral forces in both directions. Conventional cages of the above mentioned kind are made from pressed sheet metal halves which are riveted together into complete cages. Such cages are stiff, which accentuates the cage force problems caused by the above mentioned phenomena.
Some of the problems can theoretically be overcome by increasing the play between the rolling element and the cage, but too great a play is undesirable for other reasons, and thus such a measure is unsuitable.
It is known to make cages from partly a mainly rigid material with a great play between the rolling elements and partly a resilient material which encloses and contacts the rolling elements (ref. U.S. Pat. No. 2,550,912) as well as to make cages from a resilient material and surround the rolling elements by a portion of a mainly rigid material (ref. U.S. Pat. No. 2,550,911), whereby the distances between the rolling elements are permitted to vary to a certain extent. Such cages made of different materials are, however, expensive and complicated.
A cage made in one piece in which the rolling elements are snapped into position by being pressed axially from one side of the cage and in which there are resilient cage portions between the rolling element positions is known (ref. DE Offenlegungsschrift No. 2,504,741). Such a cage is assymmetrical and tends to be deformed at high rotational speeds. It can squeeze the rolling elements so that they are braked when the cage is deformed or subjected to axial forces in the bearing. The cage may even be axially expelled from the bearing during operation.